Varanus (Hapturosaurus)

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Varanus (Hapturosaurus)
Lizards Alive - Fernbank Museum - Atlanta - Flickr - hyku (18).jpg
Green tree monitor (Varanus prasinus)
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Family: Varanidae
Genus: Varanus
Subgenus: Hapturosaurus
Bucklitsch, Böhme  [ de ], and Koch, 2016
Type species
Varanus prasinus
Schlegel, 1844
Species

Hapturosaurus, sometimes known as the tree monitors, is a subgenus of lizards, consisting of slender-bodied arboreal monitor lizards mostly found in the tropical rainforests of Indonesia and Papua New Guinea.

Contents

Taxonomy

The type species is the green tree monitor, originally designated by Hermann Schlegel in 1844 as Monitor prasinus. Robert Mertens placed tree monitors within the subgenus Odatria in 1942. In 1988, tree monitors were instead placed within Euprepriosaurus alongside the mangrove monitors. [1] Nevertheless, there was a distinction between mangrove and tree monitors that was clear even then, so Euprepriosaurus was commonly considered to consist of two species complexes, i.e., the V. indicus complex and the V. prasinus complex. In 2016, Yannick Bucklitsch, Wolfgang Böhme, and André Koch found the two species complexes sufficiently morphologically, ecologically, and biologically distinct, and so all species within the V. prasinus complex were moved under a newly erected subgenus, i.e., Hapturosaurus. Hapturosaurus diverged from Euprepriosaurus during the late Miocene. [2]

Etymology

The name Hapturosaurus is derived from the Greek words "haptein" (to grasp), "ouros" (tail), and "sauros" (lizard), in reference to the prehensile tails of tree monitors. [2]

Ecology

Behaviour

All species are highly arboreal. In captivity, tree monitors demonstrate the capacity to play, in the form of destructive behaviour such as systematically shredding the leaves on plants with teeth and claws. [3] Play-like behaviour is also documented in other less closely related monitor species, such as Komodo dragons. [4]

Feeding habits

Tree monitors are primarily insectivorous, but also consume other small invertebrates such as spiders, or occasionally small mammals, lizards or the nestlings and eggs of birds. In captivity they are occasionally seen eating plants although the gut contents of wild individuals were not reported to contain plant matter. [5] This may however be a result of accidentally ingesting leaves when playing with them, which is documented in captivity. [3]

Captive hatchling often refuse food for more than two weeks, although force feeding may be recommended before then and until they begin feeding by themselves. [5]

Like other monitor lizards, tree monitors are highly intelligent reptiles, but tree monitors demonstrate particularly complex problem solving abilities, fine motor coordination, and skilled forelimb movements when hunting prey. When they cannot reach prey in tight crevices and holes with their jaws, they instead extract prey by reaching for it with their forelimbs—which are some of the longest and most slender forelimbs of all monitors and end in elongated digits tipped with large claws and adhesive soles—and hooking it out with its claws, allowing them to exploit a wider range of niches. [6] [7] [8] [9]

It is recommended that in captivity this behaviour be encouraged by placing food items in places that are only accessible by reaching for them with their forelimbs, as a form of enrichment. [6]

Range

Most species are allopatric and confined to single islands in Indonesia and Papua New Guinea, with the exception of the canopy goanna which is endemic to northeast Australia and the green tree monitor which has a much wider distribution than other tree monitors. The green tree monitor has even been purportedly sighted on the Cape York Peninsula on multiple instances, which if true would make it sympatric with the canopy goanna. [10]

Their colonization of the Indo-Pacific islands occurred during the Pleistocene glacial periods, when lower global sea levels caused the Sahul Shelf to form a continuous land-bridge out of the shallow waters around the Torres Strait Islands. This allowed the exchange and dispersal of fauna between New Guinea and Australia each time the land-bridge formed. [10]

Venom

Like all other monitor lizards, tree monitors possess venom glands in their lower jaws, giving them a noticeably venomous bite. [11] The venom is an anticoagulant, and has two known mechanisms for disrupting blood clotting: by fibrinogenolysis (the destructive cleavage of fibrinogen) and by blocking platelet aggregation. The venom also causes hypotension. Monitor lizard venom is extremely complex and diverse due to the great range of ecological niches that they occupy. [12]

Emerald tree monitor skull. Varanus prasinus skull (cropped).png
Emerald tree monitor skull.

Tree monitors have the most potently fibrinogenolytic venoms of all monitor lizards, matched only by the also arboreal banded monitor from the subgenus Odatria . This may be because arboreal monitor species experience strong selection pressure to quickly subjugate prey items before they break free and escape by falling out of the trees or flying away. As fibrinogenolytic activity is not painful, the venom likely has a primarily predatory role in subjugating prey, instead of acting as a predator deterrent. [12]

It is suggested that higher prey escape potential may cause increased venom potency, as the lethally toxic eastern green mamba and boomslang are also arboreal. This may also apply to the piscivorous and highly venomous cone snails, given their highly mobile fish prey. [12]

As the venom is an anticoagulant, monitor lizard bites often bleed far more than what the mechanical damage of the bite alone would have induced. [12]

Species

SpeciesTaxon AuthorCommon NamePicture
V. beccarii Doria, 1874black tree monitor BlackMonitor02.jpg
V. boehmei Jacob, 2003golden-spotted tree monitor Varanus-boehmei.jpg
V. bogerti Mertens, 1950Bogert's monitor
V. keithhornei Wells & Wellington, 1985canopy goanna
V. kordensis A.B. Meyer, 1874Biak tree monitor Young captive Kordo Tree Monitor.jpg
V. macraei Böhme & Jacobs, 2001blue tree monitor Varanus macraei - Reptilium Landau 01.jpg
V. prasinus Schlegel, 1839green tree monitor Varanus prasinus Oslo.jpg
V. reisingeri Eidenmüller & Wicker, 2005yellow tree monitor Lezard (Varanus reisingeri).jpg
V. telenesetes Sprackland, 1991mysterious tree monitor

Related Research Articles

<span class="mw-page-title-main">Varanidae</span> Family of lizards

The Varanidae are a family of lizards in the superfamily Varanoidea and order Anguimorpha. The family, a group of carnivorous and frugivorous lizards, includes the living genus Varanus and a number of extinct genera more closely related to Varanus than to the earless monitor lizard (Lanthanotus). Varanus includes the Komodo dragon, crocodile monitor, savannah monitor, the goannas of Australia and Southeast Asia, and various other species with a similarly distinctive appearance. Their closest living relatives are the earless monitor lizard and Chinese crocodile lizard. The oldest members of the family are known from the Late Cretaceous of Mongolia.

<span class="mw-page-title-main">Monitor lizard</span> Genus of reptiles

Monitor lizards are lizards in the genus Varanus, the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and one species is also found in the Americas as an invasive species. About 80 species are recognized.

<span class="mw-page-title-main">Megalania</span> Largest non-mosasauroid species of lizard (extinct)

Megalania is an extinct species of giant monitor lizard, part of the megafaunal assemblage that inhabited Australia during the Pleistocene. It is the largest terrestrial lizard known to have existed, reaching an estimated length of 3.5 to 7 metres, and weighing between 97–1,940 kg (214–4,277 lb), but the fragmentary nature of known remains make estimates highly uncertain.

<span class="mw-page-title-main">Perentie</span> Species of lizard

The perentie is a species of monitor lizard. It is one of the largest living lizards on earth, after the Komodo dragon, Asian water monitor, and the Crocodile monitor. Found west of the Great Dividing Range in the arid areas of Australia, it is rarely seen, because of its shyness and the remoteness of much of its range from human habitation. The species is considered to be a least-concern species according to the International Union for Conservation of Nature.

<span class="mw-page-title-main">Lace monitor</span> Species of lizard

The lace monitor, also known as the tree goanna, is a member of the monitor lizard family native to eastern Australia. A large lizard, it can reach 2 metres (6.6 ft) in total length and 14 kilograms (31 lb) in weight. The lace monitor is considered to be a least-concern species according to the International Union for Conservation of Nature.

<span class="mw-page-title-main">Black tree monitor</span> Species of reptile

The black tree monitor or Beccari's monitor is a species of lizard in the family Varanidae. The species is a relatively small member of the family, growing to about 90–120 cm (35–47 in) in total length. V. beccarii is endemic to the Aru Islands off New Guinea, living in an arboreal habitat. The skin color of adults is completely black, to which one common name refers.

<i>Varanus timorensis</i> Species of lizard

Varanus timorensis, the Timor monitor or spotted tree monitor, is a species of small monitor lizards native to the island of Timor and some adjacent islands.

<span class="mw-page-title-main">Emerald tree monitor</span> Species of lizard

The emerald tree monitor or green tree monitor, is a small to medium-sized arboreal monitor lizard. It is known for its unusual coloration, which consists of shades from green to turquoise, topped with dark, transversedorsal banding. This coloration helps camouflage it in its arboreal habitat. Its color also makes the emerald tree monitor highly prized in both the pet trade and zoos alike.

<span class="mw-page-title-main">Peacock monitor</span> Species of lizard

The peacock monitor, also known commonly as Auffenberg's monitor, is a species of small monitor lizard in the family Varanidae. The species, which belongs to the subgenus Odatria, is endemic to Rote Island, Indonesia.

<span class="mw-page-title-main">Golden-spotted tree monitor</span> Species of lizard

The golden-spotted tree monitor, also known commonly as the golden speckled tree monitor, is a species of monitor lizard in the family Varanidae. The species is endemic to Waigeo Island in Indonesia.

<span class="mw-page-title-main">Turquoise monitor</span> Species of lizard

The turquoise monitor is a species of monitor lizards found in Indonesia. Specifically, it is found on Halmahera Island and in the Maluku Islands.

<span class="mw-page-title-main">Blue-tailed monitor</span> Species of lizard

The blue-tailed monitor, blue-tailed tree monitor or Kalabeck's monitor, is a monitor lizard of the Varanidae family. It belongs to the V. doreanus group of the subgenus Euprepiosaurus.

<span class="mw-page-title-main">Black-palmed rock monitor</span> Species of lizard

The black-palmed rock monitor is a member of the Varanidae family found in Australia. Also known as the twilight monitor or the long-tailed rock monitor, it is a member of the subgenus Odatria, and is found in the northern part of Australia in the Northern Territory and Western Australia, as well as Queensland. Specifically, its distribution extends from Mount Isa in the east to the Kimberleys in the west. Its habitat is areas of rock escarpment, and large populations may be found in small areas.

Varanus keithhornei, commonly known as the canopy goanna, Keith Horne's monitor, blue-nosed tree monitor, or Nesbit River monitor, is a species of monitor lizards native to northeast Australia. It is a member of the Varanus prasinus species group.

The Rennell Island monitor is a species of monitor lizards found in the Solomon Islands archipelago. It is also known as the Hakoi Monitor. It belongs to the subgenus Euprepiosaurus along with the canopy goanna, the peach-throated monitor, Kalabeck's monitor, and others.

<i>Varanus kordensis</i> Species of lizard

Varanus kordensis, the Biak tree monitor, is a member of the Varanidae family found on Biak Island in Indonesia. It is also known as the Kordo tree monitor. Long considered a subspecies of the emerald tree monitor, most authorities now treat it as a separate species.

<i>Varanus macraei</i> Species of monitor lizard

Varanus macraei, the blue-spotted tree monitor or blue tree monitor, is a species of monitor lizard found on the island of Batanta in Indonesia. It is named after herpetologist Duncan R. MacRae, founder of the reptile park Rimba on Bali.

<i>Varanus spinulosus</i> Species of lizard

Varanus spinulosus, the Solomon Island spiny monitor, Isabel monitor, or spiny-neck monitor, is a species of monitor lizard. It is endemic to the Solomon Islands archipelago and is also known from Santa Isabel Island, San Jorge Island and Bourgainville Island.

<i>Varanus <span style="font-style:normal;">(</span>Odatria<span style="font-style:normal;">)</span></i> Subgenus of reptiles

Odatria, commonly known as dwarf monitors, consists of small monitor lizards found in Australia and Indonesia. Species in this subgenus include the smallest monitor species in the world, the tiny 16 gram Dampier Peninsula monitor, but also includes some more medium sized species such as the 240 gram black-palmed rock monitor.

<span class="mw-page-title-main">Banded tree monitor</span> Species of lizard

Varanus scalaris is a small species of monitor lizard. It is often referred to as the banded tree monitor or the spotted tree monitor.

References

  1. Böhme, Wolfgang (2003). "Checklist of the living lizards of the world (family Varanidae)" (PDF). Zoologische Verhandelingen. 341: 4–43.
  2. 1 2 Bucklitsch, Yannick; Böhme, Wolfgang; Koch, André (2016-08-17). "Scale morphology and micro-structure of monitor lizards (Squamata: Varanidae: Varanus spp.) and their allies: implications for systematics, ecology, and conservation". Zootaxa. 4153 (1): 1–192. doi:10.11646/zootaxa.4153.1.1. PMID   27615821.
  3. 1 2 Kane, Daniel (2019-10-01). "Play behaviour by captive tree monitors, Varanus macraei and Varanus prasinus". Herpetological Bulletin. 149 (Autumn 2019): 28–31. doi: 10.33256/hb149.2831 . ISSN   1473-0928.
  4. "Reptiles: Such jokers, those Komodo dragons". Science News. 162 (5): 78. 2002. doi:10.1002/scin.5591620516. ISSN   1943-0930.
  5. 1 2 Fischer, Dennis (December 2012). "Notes on the Husbandry and Breeding of the Black Tree Monitor Varanus (Euprepiosaurus) beccarii (Doria, 1874)" (PDF). BIAWAK Journal of Varanid Biology and Husbandry. 6: 79–87.
  6. 1 2 Mendyk, Robert; Horn, H.-G (2011-09-01). "Skilled forelimb movements and extractive foraging in the Arboreal monitor lizard Varanus beccarii (Doria, 1874)". Herpetological Review. 42: 343–349.
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  8. #ZooEnrichment: Green Tree Monitor at the Smithsonian's National Zoo , retrieved 2021-06-26
  9. Challenging my TREE MONITORS | WHACK-A-ROACH, SPIN THE BOTTLE + more! , retrieved 2021-06-26
  10. 1 2 Koch, Andre; Eidenmüller, Bernd (2019-08-01). "Is the New Guinea Emerald Tree Monitor Lizard (Varanus prasinus) Native to Mainland Australia?". Biawak. 13: 32–42.
  11. Fry, Bryan G.; Wroe, Stephen; Teeuwisse, Wouter; Osch, Matthias J. P. van; Moreno, Karen; Ingle, Janette; McHenry, Colin; Ferrara, Toni; Clausen, Phillip; Scheib, Holger; Winter, Kelly L. (2009-06-02). "A central role for venom in predation by Varanus komodoensis (Komodo Dragon) and the extinct giant Varanus (Megalania) priscus". Proceedings of the National Academy of Sciences of the United States of America. 106 (22): 8969–8974. Bibcode:2009PNAS..106.8969F. doi: 10.1073/pnas.0810883106 . PMC   2690028 . PMID   19451641.
  12. 1 2 3 4 Dobson, James S.; Zdenek, Christina N.; Hay, Chris; Violette, Aude; Fourmy, Rudy; Cochran, Chip; Fry, Bryan G. (2019-05-07). "Varanid Lizard Venoms Disrupt the Clotting Ability of Human Fibrinogen through Destructive Cleavage". Toxins. 11 (5): 255. doi: 10.3390/toxins11050255 . PMC   6563220 . PMID   31067768.